1. Field of the Invention
The present invention relates to a structure of an antenna-integrated microwave-millimeter wave module and particularly to a microwave-millimeter wave module integrated with a slot antenna having improved antenna efficiency and directivity.
2. Description of the Background Art
With recent increase in information amount, radio communication by high frequencies like microwave and millimeter wave has been attracting attention as high-speed and high-capacity data transmission means. This type of communication requires an antenna and a microwave-millimeter wave circuit that are integrated, i.e., an antenna-integrated microwave-millimeter wave circuit of small size, lightweight and high performance to serve as a transmitter-receiver.
Conventional slot antennas are structured by providing a slot placed opposite an open end of a strip conductor of a microstrip line with a dielectric therebetween and electromagnetically coupling the microstrip line and the slot.
FIGS. 6 and 7 show a cross section of a multilayer substrate illustrating a conventional slot antenna. Referring to FIG. 6, the multilayer substrate includes a through hole 101, a connection conductor 102 of a strip conductor, a stripline 103 of triplet type, a slot hole 104, and dielectric layers 105a-105d. A slot antenna employed as a radiating element and triplet stripline 103 including RF signal circuits are structured to form the multilayer substrate. Referring to FIG. 7, electromagnetic waves are radiated from slot hole 104 via the RF signal circuits as indicated by the arrow 106. Dielectric layers 105a-105d are connected by a large number of through holes 101. A large number of through holes 101 are also provided around the slot antenna (see for example IECE (Institute of Electronics and Communication Engineers) Japan National Conference Record, Vol. 3 (1982) p. 109).
The conventional slot antenna of this type has following disadvantages. Specifically, when an antenna feeding line is integrated with the RF signal circuits to form the multilayer substrate structure, many conductor connections are necessary between substrates. Further, many through holes are also required around the slot hole for connection of ground conductor plates for the purpose of restricting parallel-plate mode. Consequently, a feeding circuit has a complicated structure which makes fabrication thereof extremely difficult.
Although there is an advantage that the system size can be reduced, mismatch of impedance between the slot hole and the space deteriorates antenna efficiency in general.
The present invention, having been made with these circumstances taken into consideration, aims to provide a high-efficiency, small size and lightweight antenna-integrated microwave-millimeter wave module.
An antenna-integrated microwave-millimeter wave module according to one aspect of the present invention includes a dielectric substrate, a first conductor layer provided on the dielectric substrate and having a plurality of first holes formed therein to radiate electromagnetic waves, a first dielectric layer provided on the first conductor layer, an antenna feeding line provided on the first dielectric layer, a second dielectric layer provided on the antenna feeding line, a second conductor layer provided on the second dielectric layer and having a second hole formed therein, a third dielectric layer provided on the second conductor layer, a high-frequency circuit line provided on the third dielectric layer, and a semiconductor chip connected to the high-frequency circuit line and having a microwave or millimeter wave circuit formed. The first, second and third dielectric layers each have a thickness of xcex/4 or less, xcex representing wavelength of electromagnetic waves propagating through the dielectric layers, and the first, second and third dielectric layers have a relative dielectric constant of 10 or less.
The antenna-integrated microwave-millimeter wave module having the structure as described above includes the first, second and third dielectric layers each having a thickness of xcex/4 or less and a relative dielectric constant of 10 or lower, and accordingly the high-frequency circuit line and the antenna feeding line are electromagnetically coupled via the second hole. Then, without through hole, high frequency propagating through the high-frequency circuit line is conveyed to the antenna feeding line. The thickness of the first dielectric layer which is xcex/4 or less and the relative dielectric constant thereof which is 10 or less facilitate radiation of the high frequency propagating through the antenna feeding line to the outside via the first holes. Further, the first conductor layer formed on the dielectric substrate allows electromagnetic waves radiated from the first holes to be discharged via the dielectric substrate to the outside. The antenna efficiency can thus be improved by impedance matching between the first dielectric layer and the dielectric substrate.
Preferably, the dielectric substrate and the first conductor layer are laminated by lamination resin and the total thickness of the dielectric substrate and the lamination resin is 0.1 to 0.3 times as large as xcex.
Preferably, the lamination resin contains silicon or fluorine. When the lamination resin contains silicon, the lamination resin includes for example silicone resin.
Preferably, the dielectric substrate has a relative dielectric constant of 2 or more and 4 or less.
An antenna-integrated microwave-millimeter wave module according to another aspect of the invention includes a first conductor layer having a plurality of first holes formed therein to radiate electromagnetic waves, a first dielectric layer provided on the first conductor layer, an antenna feeding line provided on the first dielectric layer, a second dielectric layer provided on the antenna feeding line, a second conductor layer provided on the second dielectric layer and having a second hole formed therein, a third dielectric layer provided on the second conductor layer, a high-frequency circuit line provided on the third dielectric layer and electromagnetically coupled with the antenna feeding line via the second hole, and a semiconductor chip connected to the high-frequency circuit line and having a microwave or millimeter wave circuit formed. The first holes include a feed slot hole fed by the antenna feeding line and a non-feed slot hole not fed by the antenna feeding line, and distance d between the feed slot hole and the non-feed slot hole is approximately (0.5+n) xcex, xcex representing wavelength of electromagnetic waves propagating through the dielectric layers and n being an integer of at least 1.
The antenna-integrated microwave-millimeter wave module structured as described above includes the high-frequency circuit line and the antenna feeding line that are electromagnetically coupled via the second hole. Then, without through hole, high frequency propagating through the high-frequency circuit line is conveyed to the antenna feeding line to facilitate radiation of electromagnetic waves to the outside via the first holes. Electromagnetic waves that are radiated into the substrate (the dielectric layers) are partially reflected by the second conductor layer. The reflected electromagnetic waves have an inverted phase. The distanced between the feed slot hole and the non-feed slot hole is approximately (0.5+n)xcex. Therefore, electromagnetic waves are radiated from the non-feed slot hole having the same phase as that of electromagnetic waves radiated from the feed slot hole.
Preferably, n is 1.
Preferably, the antenna-integrated microwave-millimeter wave module further includes a dielectric substrate placed opposite the first conductor layer.
Preferably, the dielectric substrate has a relative dielectric constant of 2 or more and 4 or less.
Preferably, the first, second and third dielectric layers each have a thickness of xcex/4 or less, and the first, second and third dielectric layers have a relative dielectric constant of 10 or less.
Preferably, the dielectric substrate and the first conductor layer are laminated by lamination resin and the total thickness of the dielectric substrate and the lamination resin is 0.1 to 0.3 times as large as xcex.
Preferably, the lamination resin contains silicon or fluorine.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.